Tandem mill force feed forward adaptive system

ABSTRACT

A feed forward screwdown control system is provided for use in a computer-controlled rolling mill to improve mill setup for subsequent workpieces as well as for the piece being rolled. Ratio comparisons are made between the measured force and the predicted force in each stand while a piece is being rolled which together with the ratios determined from the previous rolled workpiece will provide information for causing an on-gauge product for the present workpiece.

United States Patent Inventor Andrew W. Smith, Jr.,

Mount LebanomPittsburgh, Pa. Appl. No. 728,469 Filed May 13, 1968Patented Mar. 9, 1971 Assignee Westinghouse Electric CorporationPittsburgh, Pa.

TANDEM MILL FORCE FEED FORWARD ADAPTIVE SYSTEM 18 Claims, 4 DrawingFigs.

US. Cl. 72/8, 72/16, 72/19 Int. Cl. B2lb 37/02, B2 lb 37/ l 2 FieldofSearch 72/7, 8,16

.nousnius MILL [56] References Cited UNITED STATES PATENTS 3,186,2016/1965 Ludbrook et al. 72/9 3,332,263 7/1967 Beadle et al. 72/10X3,357,217 12/1967 Wallace et a1. 72/8 Primary Examiner-Milton S. MehrAttorneys-F. H. Henson and R. G. Brodahl ABSTRACT: feed forwardscrewdowh control provided for use in a computer-controlled rolling millto improve mill setup for subsequent workpieces as well as for the piecebeing rolled. Ratio comparisons are made between the measured force andthe predicted force in each stand while a piece is being rolled whichtogether with the ratios determined from the previous rolled workpiecewill provide information for causing an on-gauge product for the presentworkpiece.

FINISHING MILL TANDEM Iii-ELL EOREIE EEED FORWARD ADAPTWE SYSTEMBACKGROUND OF THE INVENTION The present invention relates to rollingmills and, more particularly, to provision of improved setup conditionsbased on workpiece history in cooperation with an online monitoring ofpredetermined mill parameters.

In the operation of a metal reversing or tandem rolling mill, both theunloaded roll opening and the speed for each tandem mill speed are setup either by an operator or by a computer to provide successiveworkpiece (strip or plate) reduction resulting in an on-gauge finishedwork product. It may be assumed that the loaded roll opening at a standequals the stand delivery gauge since there is little or no elasticworkpiece recovery.

Because the setup conditions may be in error and, in any event, sincecertain mill parameters affect the stand loaded roll opening duringrolling and after setup conditions have been established, a stand gaugecontrol system must be employed to closely control the stand deliverygauge. Thus, at the present state of the rolling mill art, a stand gaugecontrol system is normally used for a reversing mill stand and forpredetermined stands in tandem rolling mills.

Recent experience in tandem hot strip rolling mills and reversing platemills has demonstrated that a roll force gauge control systemisrparticularly effective. Briefly, the roll force gauge control systemuses Hookes law in controlling the screwdown position at a rollingstand, i.e., the loaded roll opening under rolling conditions equals theunloaded roll opening (screwdown position) plus the mill spring stretchcaused by a separating force supplied to the rolls by the workpiece. Toembody this rolling principle in the roll force gauge control system, aload call or other force detector measures the roll separating force.The screwdown position is then controlled to balance the roll forcechanges from a reference or setpoint value and thereby hold the loadedroll opening at a substantially constant value. Once the unloadedopening and the stand speed setup are determined by either the milloperator or the mill computer for a particular workpiece pass or seriesof passes, the rolling operation is begun; the screwdowns are thencontrolled to regulate the workpiece delivery gauge from the reversingmill stand or from each roll force control tandem mill stand. For a moredetailed discussion of an automatic roll force gauge control system,reference is made to copending patentapplication filed Nov. 29, 1967,Ser. No. 686,783 entitled compatible Roll Force Gauge Control Method andApparatus for Metal Rolling Mills by Calvin W. Eggers and John Csonkaand assigned to the same assignee as the present invention. Theapplication of the principles of the above-cited reference serve tomaintain an on-gauge work produce once, the mills is full, i.e., theworkpiece is present in all stands. However, to further optimize theoperation of the above system, it is highly desirable to provide setupconditions which, in addition to providing an on-gauge rolling of thehead end of theworkpiece strip, also establish mill operating conditionswhich are compatible with the takeover of the automatic roll force gaugecontrol system once the mill becomes full. Moreover, it is intended thatgauge regulation for the head end of a workpiece strip be controlled andmonitored without provision of additional apparatus than would otherwisebe required in a roll force gauge control system.

Previously, mill setup parameters have been set either by the operatoror by a computer. But, as the rolling mill parameters have increasedboth in number and complexity, the computer has played the dominant rolein determining mill setup with the operator serving as backup. Thecredibility of the computer has been established by causing it tomonitor certain inputs according to a predetermined model and then,through functional relationships between these inputs, to provide properoperating conditions. As each workpiece is rolled, information isgathered from the various inputs which serve to improve the setupconditions for the rolling of the next workpiece. Such a system hasproved satisfactory in that, even if the original setup conditions arepoor, eventually the system will adapt to a proper setup by learningfrom the rolling of each previous workpiece. It should be noted,however, that the rolling of a workpiece is inherently dependent oninformation gained from previous rollings and that any error inconditions for that particular piece would go uncorrected for thatparticular piece.

SUMMARY OF THE INVENTION It is, therefore, a general object of thepresent invention to provide a new and improved head-end gauge controlsystem for rolling the head end of workpieces in a continuous striprolling mill.

A further object of the present invention is to provide a new andimproved head-end gauge control system wherein changes in the setupconditions for the workpiece being rolled may occur from informationreceived from the last rougher and first finishing stand of the rollingmill.

An additional object of the present invention is to provide a new andimproved head-end gauge control system wherein ratios between predictedand actual force are made at the last roughing stands and at thefinishing stands to provide setup information for rolling of the nextworkpiece.

A still further object of the present invention is to provide a new andimproved head-end gauge control system whereby subsequent stands areresponsive to feed forward information for providing an on-gaugeworkpiece strip.

Yet a further object of the present invention is to provide a new andimproved head-end gauge control system which is compatible withapparatus required in a conventional computer-controlled roll forcegauge control system.

In accordance with the general principles of the present invention, atandem strip rolling mill is under the control of a process computer forproviding an on-gauge workpiece strip. During the rolling of the headend of a workpiece, a force feed forward system is operating whereby thepattern for the head end is held in storage whereby the pattern for thehead end is held in storage ash is rolled to the last roughing stand andthen the finishing stands. Measurements are then made on the head end ofthe next piece to determine whether the general force level will behigher or lower and corrections are made in the later stand screwdownreferences to compensate for the predicted change in roll separatingforce. The target thickness to be delivered from each stand ismaintained the same as determined from the original schedule calculationso no change is required in the speed of the stands.

These and other objects of the present invention will become moreapparent upon consideration of the following detailed description alongwith the attached drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 shows a schematic diagram of the laststand of a roughing mill and a portion of the finishing mill in a tandemhot steel strip rolling mill illustrating the inputs and outputsrequisite to the head-end gauge control system which is the subject ofthis invention.

FIG. 2 represents the system operation for the rolling of a newworkpiece from the time it enters the last rougher until the entire millis full.

FIGS. 3 and i set forth the system operation in accordance with the headend of the workpiece entering certain predetermined stands within therolling mill.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. l, aportion of a continuous strip rolling mill is shown and designatedgenerally by the numeral ill. The last stand of the roughing mill isshown by the symbol R followed by the first two and the last stands of afinishing line designated respectively by the symbols El, E2 and EN Eachof the rolling stands includes a pair of work rolls l2 and M. These workrolls are caused to provide a strip reduction as the workpiece 16 passessuccessively through each of the several stands. A set of backup rolls1% and 20 provides pressure on the work rolls l2 and 14 in response tothe operation of a screwdown 22. The regulation of the applied pressureis through a screwdown motor 24 whose operation is controlled by aposition regulator 26. Screwdown position detectors 28 monitor theposition of the screwdowns 22 by detecting the number of revolutions ofthe screwdown motors 24 and transmitting an output signal representativethereof. Following the last stand FN in the finishing mill, an X-raygauge 30 is so positioned to detect the actual finished gauge of theworkpiece and to provide a signal proportional thereto. Associated witheach of the respective rolling stands is a load cell 32 which measuresthe separating roll force at each of the respective stands.

Control of the rolling process is provided by a process control computer34 which provides communication between the rolling mill inputs andoutputs in a predetermined manner. The exact mode of control is providedby an externally provided program which functionally relates an input orcombination of inputs to provide controlled output signals which arecommensurate with an on-gauge workpiece strip. The functionalrelationship between and among certain inputs as seems to exist withinthe process computer 34 will be discussed in detail herein. Otherapparatus and structure necessary for the proper operation of a rollingmill is purposely left out for ease of illustration and wouldnecessarily include such items as drive motors, potentiometers, speedcontrollers, temperature sensors etc.

Accurate online gauge control and regulation of the workpiece head endis achieved by the provision of reference signals from the processcontrol computer 34 to the respective position regulators 26corresponding to all the finishing stands when the workpiece is beingmeasured in the last rougher and the third to last finishing stands whenthe workpiece is being measured in the first finishing stand. Thereference signals are developed through a mathematical model provided inthe process control computer 34 which is responsive to the analoguesignals resulting from the respective load cells 32, the screwdownposition detectors 28, and the X-ray gauge 30 as well as digital inputspertaining to the strip characteristic shown in block 36 to effectadequate gauge control on the workpiece 316 until the mill becomes full.Once this condition has occurred the process control computer 34 is thenfree to provide control under a gauge control system as previouslyreferenced in above-referenced Eggers et al. copending patentapplication. It is only upon the beginning of the rolling of anotherworkpiece that the head-end gauge control system is again activated toprovide proper on-gauge strip until the mill is once again full. Thedigital inputs relating to the strip characteristics in block 36contains such items as strip width, desired or target gauge, and thetype of strip alloy.

Online updating of the screwdown reference signals which are fed to theposition regulators 26 is accomplished both when the workpiece entersthe last rougher and when the workpiece enters the first finisher. Thusthe screwdown for all of the succeeding stands are updated twice in aonline fashion within the rolling cycle of the workpiece presently inthe rolling mill. Then, once the workpiece has traversed to the laststand in the finishing mill, the screwdown reference signals are againupdated to reflect the difference between the predicted and actual gaugeof the workpiece at the point where gauge regulation of the head-endfinishes and the gauge control program for the mill once full takesover.

Referring now to FIG. 2 a flow chart illustrating the timing sequence ofthe head-end gauge control system is illustrated. System operation isinitiated at the start block 109 at some time as the workpiece isprogressing through the roughing mill. As the workpiece is beingsuccessively reduced in the roughing mill, the last rougher isinterrogated in block 110 to see if the workpiece has entered therougher R. If not a finite delay period is initiated in block 12'!)whereupon a return is then made to block 110 to again interrogate to seeif the workpiece has now entered the last rougher. Once the workpiece 16has reached the last rougher stand R of FIG. 1 and is detected by aseparating force which acts against the corresponding load cell 32 toprovide a signal to the process control computer, a counter in theprocess control computer 34 which represents the stand number is set inblock to the stand number corresponding to the last rougher R whereuponthe system then progresses to that part of the gauge control systemcorresponding to updating of the screwdown references while in the lastroughing stand. This function is illustrated in block by referring tothe routine as shown in FIG. 3 progressing from the enter blockproceeding through the exit block and then returning to block which theninterrogates the first finishing stand F1 to determine whether theworkpiece has entered. If not, a finite delay is initiated in blockfollowing which return is made to block 140 for a further interrogationof the first finishing stand F1. When the workpiece is detected in thefirst finisher, the stand counter in the process control computer 34 isthen set to the stand number for the first finisher in block as aprelude to again traversing through the system of FIG. 3 as shown inblock which provides updating of the screwdown following the entry ofthe workpiece into the first finishing stand Fl.

Following the adjustments or updating of the screwdown references afterthe workpiece has entered the first finishing stand 2 it is thennecessary to determine when the workpiece has entered the last finisheras shown in block 180. If the workpiece has yet to enter the lastfinishing stand FN, a finite delay system is set up in block 190 whichthen returns to block for further interrogation. Once the workpiece hasbeen detected, the stand counter n is then set in block 201 to the standnumber for the first finishing stand for a final updating in block 211by referring to the routine as set forth in FIG. 4 which is the finalupdating procedure for the screwdowns and provides the setup referencesfor the next workpiece to be rolled. Once the workpiece has traversedthrough the last finishing stand, the mill is then considered full andcontrol is then transferred to some roll force automatic gauge controlsystem such as that previously mentioned in the abovereferenced Eggerset al. copending patent application.

FIG. 3 illustrates the operation of the head-end gauge control system atsuch times when the workpiece has either entered the last rougher standR or the first finisher stand Fl. As previously mentioned this occurs atthe blocks 130 and 170 of FIG. 2. The first block of FIG. 3 is block 200which is the entry point to this segment of head-end gauge controlsystem. At this time the stand counter is set to the proper standnumber. In block 202 the stand is interrogated to see if it is actuallyproducing a reduction in the strip gauge or on the other hand if it ismerely providing a dummy operation. Providing that the stand n isoperating properly, in block 204 the mill spring is calculated using themeasured force FMn as determined from the load cell 32 corresponding tothe stand number in the counter n. The mill spring Xn is equal to thenegative of the fraction F, /I( where F, is the measured force and K isequal to the mill spring constant. for that particular stand. A morecomplete description and discussion of the mill stretch is to be foundin the previously referenced Eggers et al. patent application. Apreviously determined screwdown offset OS, which acts as a correctionfactor to steady state gauge errors is then added to the just-calculatedmill spring K and the screwdown position SDM, as determined by thescrewdown position detector 28 of FIG. 1 to provide a calculated gauge Hwhich corresponds to the actual thickness or the workpiece deliverygauge of the stand n. This calculation is represented by the block 206.Block 208 then predicts a force F corresponding to the stand in as afunction of the entry gauge Pi the delivery gauge H the width of thestrip W, and the strip temperature T Had the stand :1 been inoperable asdetermined in block 202 the exit gauge would then have been set equal tothe entry gauge as shown in block 210. Blocks 202 through 210 areinitiated each time that data has been collected on the head end of theworkpiece in either the last rougher stand R or the first finishingstand F1. in this procedure, any difference between the measured rollforce and screwdown setting and the predicted roll force and screwdownsetting will cause a difference between the actual gauge delivered fromthe stand and the desired gauge. Blocks 2% through 210 calculate thescrum gauge delivered from the particular stand and repredict the railseparating force for the actual draft taken in that stand. Once thepredicted force i has been predicted, interrogation is made in block 21.2 to determine whether the stand counter is set for the last rougherstand or the first finishing stand. Providing that the stand number n isequal to that of the last rougher, interrogation is made in block 214 todetermine whether the piece now being rolled is of the same alloycontent as the previous piece. Providing the workpiece has the samealloy content, a check is made in block 216 to determine whether theratio of the final target gauge l-lT for the previous piece to the finaltarget gauge l-lT,,-, of the previous piece is within percent. if thelimit check in block 216 is satisfied,

. the procedure then follows to block 226 for a calculation of forcecorrection factor. Referring now to block 214, if the present piecebeing rolled is a different alloy from that of the last piece, the standcorrection factor SCFn is set equal to l for all stands. The sameprocedure is followed if the limit condition suggested in block 216 isnot satisfied.

Since the stand counter n is now equal to that of the first rougher, theaction of block 213 serves to set the stand correction factor for thelast rougher equal to l in block 220 the stand counter is. interrogatedto see if it is presently equal to the stand number of the last finisherand if not the stand number n is increased by l in block 222 and returnis then made to block 218 which then sets the current stand correctionfactor equal to-l This same process continues until the last finisher isdetected in block 2258 whereupon the stand number is again set to itsinitial position as that of the last rougher in block 224. Thus, it isseen that if the present workpiece being rolled is different in alloy oreven having the same alloy is significantly different in desired targetgauge the stand correction factor for all the finishing stands are resetto l and are not dependent on any past history.

Once a current set of stand correction factors corresponding to each ofthe finishing stands has been developed, it is now possible to compute aforce correction factor FCF which is equal to the fraction (FMJI CFM(E). if the force correction factor is within percent as determined inblock 228 the procedure is then continued in block 23 However, shouldthe force correction factor be outside the 25 percent limit, it is setequal to 1 in block 232 before preceeding to the next sequential block234. Assuming that the stand counter n is equal to the stand number forthe last rougher as determined in block 2% the stand counter would beincreased by l in bloclt 244i and now be equal to the stand number forthe first finisher. if this stand is operating and not dummied asdetermined in block sea, the force E}. is then repredicted in block 244using the force correction factor FCF calculated from the last rougherthe stand correction factor SCF determined from the previous piecerolled and the last predicted force F,,. Then, with the forcerepredicted for stand n the mill spring for stand n is then recalculatedusing this predicted force in block are. A new and updated screwdown isthen determined in block M5 by subtracting from the predicted gauge HPthe mill spring X as a function of the predicted force F and thepreviously determined offset factor OS,,. This screwdown reference isthen representative of the reference signal which should then beprovided to the position regulator 26 for the first finishing stand Flof H6. 1. in block 254i the stand number n is then interrogated todetermine whether it is at that of the last finish stand FN and if so,the procedure is completed at block 252. However, in this case since itis only equal to the of the first finishing stand the stand number isincreased by l in block 2 30 and a determination as to whether thesecond finishing stand is operating as made in block 242. Itnecessariing finishing stands in the mill. For any finishing stand thatis inoperable as determined in block 242 the stand number is increasedby l in block 254 and no updated screwdown reference is calculated forthat inoperative stand.

Now referring to FIG. 2, block 1176 again calls for the return to thesystem procedure of H6. 3 with the only difference being that the standnumber n is now equal to that of the first finishing stand Fl. The sameprocedure beginning at block 200 is followed as when n was equal to thestand number of the last rougher except that beginning in block 2R2, ifthe stand number is equal to that of the first finisher the procedureimmediately skips to block 226 for calculation of a force correctionfactor without providing any recomputation of the stand correctionfactor. Thus it is apparent that for all future computations the standcorrection factor SCF will remain as calculated previously from thesystem sequence when the mill was full on the previous piece. A secondvariance in the procedure occurs following the computation of the forcecorrection factor whereupon in block 234 n is now equal to the standnumber for the first finisher and proceeds to block 255 which increasesthe stand number by l and is thus now equal to that of the secondfinishing stand F2. if the second finishing stand is not in operation asdetermined in block 256 the procedure advances immediately to block 2%where new roll force and screwdown setting are determined for theremaining finishing stands as previously described. If, however, thesecond finishing stand is in operation as determined in block 256 themill spring is again recalculated in block 258 using the predicted forceF,,. Then, in block 260 gauge thickness 1H,, is predicted out of thenext stand using the unadjusted screw setting. This is done becausethere is not sufficient time to be sure that the second stand would bereset to a new value before the strip enters the rolls. The computationinvolved is set forth in detail in block 260 wherein l-lT equals thetarget exit gauge from the present stand and ll-lT,,-, equals the targetentry gauge at the present stand. The stand number is again increased byl in block 262 and a check is made in block 264 to see if this new standis operating. If the stand is inoperable, the stand number is againincreased and interrogated until some stand number is found to beoperating. Having found an operable stand, in block 266 a roll force Fis predicted using the predicted entry H 'q and the target exit gaugeET,, the force correction factor PCP and the stand correction factorSCF,,. Once a new predicted force has been computed the procedureproceeds to block 246 and continues as previously described for the lastroughing stand.

Again referring to H0. 2, block 211 makes reference to the systemprocedure of FIG. 4 when the stand number has been set to that for thefirst finishing stand Fl. It should be noted that in FIG. 41 blocks 2%through Zill are exactly equivalent to that of FIG. 3 and serve topredict a force for that particular stand n in block 302 an offsetfactor OS,, is calculated-for stand n which corresponds to a correctionfactor for offsetting the setting gauge error. Once the offset 08,, iscomputed, stand n is then interrogated in block 3% to see if it isoperating. If not, no new stand correction factor is provided and inblock 312 interrogation is made as to whether n is equal to the numberof the last finishing stand. if not in block 311 the stand number isincreased by 1 and the entire procedure is repeated beginning at block2m until a new predicted force F and a stand correction factor SCF iscomputed for all the finishing stands. On the other hand, providing thatthe stand it was in operation as determined in block 394 a temporarycorrection factor is computed according to the relationship block 3%.This temporary correction factor TCF is then checked to be within a 25percent limit in block 30% and if so, in block 310 the temporarycorrection factor is then set equal to the new stand correction factorSCF lf the temporary correction factor TCF, is without the predeterminedlimits as determined in block 30%, the procedure immediately proceeds toblock 312 which then proceeds to the next finishing stand leaving theprevious stand correction factor unaltered. Once the last stand hasreceived a new stand correction factor as determined in block 312, theprocedure is finished in block 314 and returned to begin the roll forceAGC system as seen in FIG. 2.

It should be noted that the calculations for offset in block of FIG. 4may either be calculated at this time or as a part of the roll force AGCsystem itself once the mill is full. A more complete and detaileddescription of providing an accurate offset is set forth in copendingpatent application Ser. No. 677,308 filed Oct. 23 1967 and entitledScrewdown Offset System and Method for Improved Gauge Control" by AndrewW. Smith, Jr., and assigned to the same assignee as the presentinvention.

In summary this invention provides a system and method of making forcemeasurement in all of these stands in a rolling mill as a piece is beingrolled. Ratio comparisons are made between the measured force in eachstand and predicted force and these ratios are then used to betterpredict forces for the rolling of the next workpiece. In addition, themeasured force in an early stand as the next piece is being rolled iscompared with the predicted force and this ratio along with the ratioscalculated for each stand while rolling the previous piece are used tobetter predict the force roll opening to thus obtain a good mill setupand produce a proper on-gauge finish workpiece.

Since additional changes not herein specifically referred to may be madein the above-described system such as increasing or decreasing the limitchecks, and different embodiments of the invention could be made withoutdeparting from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingshall be interpreted as illustrative only and not in a limiting sense.

I claim:

1. A gauge control system for a rolling mill having at least one rollstand with a screwdown-controlled roll opening through which a firstpass of a present workpiece is transported, said system comprising:

means for detecting the actual roll force at said one roll stand duringsaid first pass;

means for determining the delivery work piece gauge leaving said rollstand after said first pass;

means for determining a predicted roll force for said first pass inrelation to said delivery workpiece gauge;

means for determining a correction factor for a second pass of saidpresent workpiece through a roll stand in accordance with a ratio ofsaid actual roll force to said predicted roll force;

means for determining a screwdown setting in accordance with saidcorrection factor for said second pass through a roll stand of saidrolling mill; and

means for controlling the screwdown movement for said second pass inaccordance with said screwdown setting to effect a desired reduction inthe gauge of said present workpiece.

2. The gauge control system as set forth in claim 11, wherein saidsystem includes:

recording means for retaining the detected actual roll force at a rollstand during said first pass;

means for determining the delivery workpiece gauge for each pass of theworkpiece through a roll stand of said rolling mill; and

means for determining if said present workpiece is difierent from aprevious workpiece in relation to one of the alloy and the target gaugeof said present workpiece for providing a unity stand correction factorwhen such a difference is determined.

3. The gauge control system as set forth in claim 1, wherein said gaugecontrol system is operative during the rolling of the head end of saidpresent workpiece.

4. The gauge control system as set forth in claim 1, including means fordetermining a respective stand correction factor for each of said rollstands in accordance with the equation SCF where SCF is the determinedstand correction factor for stand n, FM, is the measured force relativeto a present work piece passing through stand n and F, is the predictedforce for stand n in accordance with the actual reduction in the gaugeof the present workpiece made by stand n and wherein said standcorrection factor SCF, is used to determine the respective stand nscrewdown movement relative to a subsequent workpiece similar to saidpresent workpiece.

5. The gauge control system as set forth in claim 1, including means fordetermining a correction factor according to the equation FCF (SCF) (F)where FCF is the determined force correction factor for subsequentpasses of said present workpiece, FM is the measured roll force of saidone roll stand during said first pass of the present workpiece throughsaid stand SCF is the stand correction factor in relation to a previoussimilar workpiece for said one roll stand, and F is the predicted rollforce for said one roll stand in accordance with the actual reductionmade in the gauge of the present workpiece by said stand, and whereinsaid correction factor is used to determine the respective correctivescrewdown movements for subsequent passes in relation to said presentworkpiece.

6. The gauge control system as set forth in claim 4, including means forproviding a unity stand correction factor SCF, for stand n when saidsubsequent workpiece is one of a different alloy and a different targetgauge in relation to said present workpiece.

7. The gauge control system as set forth in claim 1, including means forproviding a unity correction factor when said correction factor isoutside predetermined limits.

8. A workpiece gauge control system for a rolling mill having at leastone roll stand with a screwdown controlled roll opening and into which aworkpiece is passed, said system comprising:

means for sensing the actual roll force at said one roll stand during afirst pass of said workpiece through said one roll stand;

means for determining the actual reduction taken in the gauge of saidworkpiece during said first pass through said one roll stand;

means for determining a predicted roll force for said one roll stand inaccordance with said actual reduction during said first pass;

means for determine a correction factor in accordance with a ratio ofsaid actual roll force to said predicted roll force, and

means determining determining a screwdown movement at least a secondpass of said workpiece through a roll stand of force; rolling mill, withthe latter said means being responsive to said correction factor fordetermining the screwdown movement for at least said second pass.

9. The guage control system as set forth in claim 8, including screwdowncontrolling means to effect a corrective screwdown movement inaccordance with said correction factor for at least a second pass ofsaid workpiece through a roll stand during the rolling of the head endof said workpiece.

10. The gauge control system as set forth in claim 8 wherein said meansfor determining a predicted roll force includes a digital computer, saidcomputer having an input coupled to said actual roll force sensing meansand an output coupled to said means for determining a screwdownmovement.

11. The gauge control system as set forth in claim 8,.with said meansfor detennining a correction factor being operative according to theequation FM X Y where FCF is the determined correction factor, FM is thesensed roll force relative to a present workpiece for said one rollstand, SCF is the stand correction factor determined for a previoussimilar workpiece prior to said present workpiece being loaded into saidone roll stand, and F is the predicted force relative to said first passof the present workpiece through said one roll stand.

112. The gauge control system as set forth in claim 8 including meansfor providing a unity correction factor when said correction factor isbeyond predetermined value limits.

R3. in a workpiece thickness control system for a rolling mill having atleast one roll stand with a controlled roll opening and into which aworkpiece is passed, the combination of:

means for sensing the actual roll force of said one roll stand of saidrolling mill during a first pass of said workpiece through said one rollstand;

means for determining the actual delivery thickness of said workpieceafter said first pass;

means for determining a predicted roll force for said first pass inaccordance with the actual delivery thickness of said workpiece aftersaid first pass;

means for determining an operation correction factor in accordance witha ratio between said actual roll force during said first pass and saidpredicted roll force during said first pass; and

means responsive to said operation correction factor for determining theroll opening for a subsequent pass of said workpiece through a rollstand of said rolling mill.

M. The control system of claim 13; with said means for determining theroll opening of a roll stand being operative to effect a desiredreduction in the thickness of the head end of said workpiece during saidsecond pass,

lid. in the method of controlling the operation of a rolling mill forreducing the thickness of a workpiece, said rolling mill including atleast one roll stand having a roll opening established in advance of afirst pass of said workpiece through said one roll stand of said rollingmill, the steps of:

sensing the actual roll force during said first pass of said workpiecethrough said one roll stand;

establishing the actual reduction made in the thickness of saidworkpiece during said first pass;

establishing a predicted roll force in accordance with the reductionmade in the thickness of said workpiece during said first pass of theworkpiece through said one roll stand;

establishing an operation correction factor in accordance with a ratioof said actual for roll force and said predicted roll force; and

establishing in accordance with said correction factor the roll openingof a roll stand of said rolling mill for a second pass of the workpiecethrough the latter roll stand.

16. The method of claim 15, operative with particularly the head end ofsaid workpiece.

17. The method of claim 15 operative with a rolling mill 18. Theworkpiece thickness control system of claim 13, in-

cluding:

means for sensing the actual roll force of the last said roll standduring an earlier pass of a previous workpiece through the latter rollstand;

means for determining a predicted roll force for said earlier pass inaccordance with the actual delivery thickness of said previous workpieceafter said earlier pass;

means for determining a stand operation correction factor for the latterroll stand in accordance with a ratio between the earlier pass actualroll force and the earlier pass predicted roll force relative to saidprevious workpiece with said means for determining the roll openingbeing responsive to said stand operation correction factor whendetermining the roll opening of the latter roll stand.

Patent No.

lnventor(s) Andrew Dated March 9, 97

W. Smith, Jr.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column Column Column Column Column Column Column Column Column ColumnColumn Column Column Column Column Column Column Column Column ColumnColumn Column Column Column Column referenced line 53, line 57, line 61,

calculated line 62, line 63, line U3,

line line line line line line line 33,

"online" should be on-line "call" should be cell "compatible" should bePredictive "produce" should be product "mills" should be mill and 40,remove "whereby the pattern for head end is held in storage".

after "FN" provide a period "backup" should be back-up "online" shouldbe on-line "above-referenced" should be above on line" should be on-line'on line" should be on-line "just-calculated" should be just after"Hn-l" provide a comma. after "Hn" rovide a comma. "%FMn)/SCFn5 (Fn)should be SCFn)(Fn) "the" should be that after "stand" provide a comma.after "HTn" provide a comma. "30" should be 302 8, before "filed"provide a comma. 8, after "23" provide a comma.

"screwdown-controlled" should be screwdown controlled line 53, line 73,

"11" should be l after the equation provide a comma.

Page 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,568,637 Dated March 9L 1971 nv n fl Andrew w. Smith, Jr.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 8, line 5, after "n" provide a comma.

Column 8, line 13, after the equation provide a comma.

Column 8, line 18, after "stand" provide a comma.

Column 8, line 50, cancel "determining", first occurrence,

and substitute for Column 8, line 50, before "at" insert for andsubstitute said provide a semicolon.

Column 8, line 52, cancel "force; Column 10, line 31, after "pieceSigned and sealed this 16th day of November 1971.

(SEAL) Attest:

EDWARD M.F'LETCHER, J'R. ROBERT GOT'ISCHALK Attesting Officer ActingCommissioner of Pete FORM F G-1050 (IO-SQ!

1. A gauge control system for a rolling mill having at least one rollstand with a screwdown-controlled roll opening through which a firstpass of a present workpiece is transported, said system comprising:means for detecting the actual roll force at said one roll stand duringsaid first pass; means for determining the delivery work piece gaugeleaving said roll stand after said first pass; means for determining apredicted roll force for said first pass in relation to said deliveryworkpiece gauge; means for determining a correction factor for a secondpass of said present workpiece through a roll stand in accordance with aratio of said actual roll force to said predicted roll force; means fordetermining a screwdown setting in accordance with said correctionfactor for said second pass through a roll stand of said rolling mill;and means for controlling the screwdown movement for said second pass inaccordance with said screwdown setting to effect a desired reduction inthe gauge of said present workpiece.
 2. The gauge control system as setforth in claim 11, wherein said system includes: recording means forretaining the detected actual roll force at a roll stand during saidfirst pass; means for determining the delivery workpiece gauge for eachpass of the workpiece through a roll stand of said rolling mill; andmeans for determining if said present workpiece is different from aprevious workpiece in relation to one of the alloy and the target gaugeof said present workpiece for providing a unity stand correction factorwhen such a difference is determined.
 3. The gauge control system as setforth in claim 1, wherein said gauge control system is operative duringthe rolling of the head end of said present workpiece.
 4. The gaugecontrol system as set forth in claim 1, including means for determininga respective stand correction factor for each of said roll stands inaccordance with the equation where SCFn is the determined standcorrection factor for stand n, FMn is the measured force relative to apresent work piece passing through stand n and Fn is the predicted forcefor stand n in accordance with the actual reduction in the gauge of thepresent workpiece made by stand n and wherein said stand correctionfactor SCFn is used to determine the respective stand n screwdownmovement relative to a subsequent workpiece similar to said presentworkpiece.
 5. The gauge control system as set forth in claim 1,including means for determining a correction factor according to theequation where FCF is the determined force correction factor forsubsequent passes of said present workpiece, FM is the measured rollforce of saId one roll stand during said first pass of the presentworkpiece through said stand SCF is the stand correction factor inrelation to a previous similar workpiece for said one roll stand, and Fis the predicted roll force for said one roll stand in accordance withthe actual reduction made in the gauge of the present workpiece by saidstand, and wherein said correction factor is used to determine therespective corrective screwdown movements for subsequent passes inrelation to said present workpiece.
 6. The gauge control system as setforth in claim 4, including means for providing a unity stand correctionfactor SCFn for stand n when said subsequent workpiece is one of adifferent alloy and a different target gauge in relation to said presentworkpiece.
 7. The gauge control system as set forth in claim 1,including means for providing a unity correction factor when saidcorrection factor is outside predetermined limits.
 8. A workpiece gaugecontrol system for a rolling mill having at least one roll stand with ascrewdown controlled roll opening and into which a workpiece is passed,said system comprising: means for sensing the actual roll force at saidone roll stand during a first pass of said workpiece through said oneroll stand; means for determining the actual reduction taken in thegauge of said workpiece during said first pass through said one rollstand; means for determining a predicted roll force for said one rollstand in accordance with said actual reduction during said first pass;means for determine a correction factor in accordance with a ratio ofsaid actual roll force to said predicted roll force, and meansdetermining determining a screwdown movement at least a second pass ofsaid workpiece through a roll stand of force; rolling mill, with thelatter said means being responsive to said correction factor fordetermining the screwdown movement for at least said second pass.
 9. Theguage control system as set forth in claim 8, including screwdowncontrolling means to effect a corrective screwdown movement inaccordance with said correction factor for at least a second pass ofsaid workpiece through a roll stand during the rolling of the head endof said workpiece.
 10. The gauge control system as set forth in claim 8wherein said means for determining a predicted roll force includes adigital computer, said computer having an input coupled to said actualroll force sensing means and an output coupled to said means fordetermining a screwdown movement.
 11. The gauge control system as setforth in claim 8, with said means for determining a correction factorbeing operative according to the equation where FCF is the determinedcorrection factor, FM is the sensed roll force relative to a presentworkpiece for said one roll stand, SCF is the stand correction factordetermined for a previous similar workpiece prior to said presentworkpiece being loaded into said one roll stand, and F is the predictedforce relative to said first pass of the present workpiece through saidone roll stand.
 12. The gauge control system as set forth in claim 8including means for providing a unity correction factor when saidcorrection factor is beyond predetermined value limits.
 13. In aworkpiece thickness control system for a rolling mill having at leastone roll stand with a controlled roll opening and into which a workpieceis passed, the combination of: means for sensing the actual roll forceof said one roll stand of said rolling mill during a first pass of saidworkpiece through said one roll stand; means for determining the actualdelivery thickness of said workpiece after said first pass; means fordetermining a predicted roll force for said first pass in accordancewith the actual delivery thickness of said workpiece after said firstpass; means for determining an operation correction factor in accordancewith a ratio between said actual roll force duriNg said first pass andsaid predicted roll force during said first pass; and means responsiveto said operation correction factor for determining the roll opening fora subsequent pass of said workpiece through a roll stand of said rollingmill.
 14. The control system of claim 13, with said means fordetermining the roll opening of a roll stand being operative to effect adesired reduction in the thickness of the head end of said workpieceduring said second pass.
 15. In the method of controlling the operationof a rolling mill for reducing the thickness of a workpiece, saidrolling mill including at least one roll stand having a roll openingestablished in advance of a first pass of said workpiece through saidone roll stand of said rolling mill, the steps of: sensing the actualroll force during said first pass of said workpiece through said oneroll stand; establishing the actual reduction made in the thickness ofsaid workpiece during said first pass; establishing a predicted rollforce in accordance with the reduction made in the thickness of saidworkpiece during said first pass of the workpiece through said one rollstand; establishing an operation correction factor in accordance with aratio of said actual for roll force and said predicted roll force; andestablishing in accordance with said correction factor the roll openingof a roll stand of said rolling mill for a second pass of the workpiecethrough the latter roll stand.
 16. The method of claim 15, operativewith particularly the head end of said workpiece.
 17. The method ofclaim 15 operative with a rolling mill having a plurality of stands,said method being operative with the head end of said workpiece anduntil said workpiece has entered all stands of said rolling mill. 18.The workpiece thickness control system of claim 13, including: means forsensing the actual roll force of the last said roll stand during anearlier pass of a previous workpiece through the latter roll stand;means for determining a predicted roll force for said earlier pass inaccordance with the actual delivery thickness of said previous workpieceafter said earlier pass; means for determining a stand operationcorrection factor for the latter roll stand in accordance with a ratiobetween the earlier pass actual roll force and the earlier passpredicted roll force relative to said previous workpiece with said meansfor determining the roll opening being responsive to said standoperation correction factor when determining the roll opening of thelatter roll stand.